In the afternoon I was lying in my bed, trying to recuperate from a horrible summer cold.Thinking randomly about various things, I thought, why do people scream when they are suddenly exposed to some danger? Also, they either try to shield their eyes or their eyes are dilated.
I think screaming is a primeval reaction that happens in all animals. It has a purpose. When you scream, you unconsciously, perhaps, try to warn the others. Screaming can be alarming and it signifies extreme danger. When a single individual or an animal screams, he or she is trying to let it be known that some grave danger has surfaced and they either have to run, or come to rescue. In most of the cases it is voluntary, so the evolution has ensured that we amplify the presence of a danger whether we want it or not.
Do you know even in extreme pain, guinea pigs don’t utter even a whimper sometimes? This is because they can neither run fast nor they can counter attack. All they can do is, remain out of vision. In order to achieve this, they need to keep quiet.
What about shielding the eyes or dilating them? I think when we shield our eyes, we just want to delude ourselves that since we cannot see the danger, it is not there. When we dilate our eyes, maybe we want to gather as much visual data as possible to get the full grasp of the situation.